Genetically engineered proteins have been gaining increased importance as potential therapeutics for human and animal health care, as well as industrial applications. Currently, such proteins are produced by several similar series of processing steps which can be generically summarized as follows: (1) Protein production by cell culture; (2) Cell breakage, extraction and removal; (3) Primary purification or initial fractionation; (4) High resolution chromatographic purification; and (5) Formulation and encapsulation. Downstream purification (steps 2-5) typically accounts for a large percent of the total production costs.
As cells are relatively expensive raw materials, high product and activity yields are of prime importance. For large scale operations, the preferred methods of cell disruption are high-pressure homogenization and wet milling in high-speed agitator bead mills. These techniques employ high shear forces and generate heat, both factors which are potentially damaging to the protein being recovered.
Furthermore, conventional industrial-scale microbial cell disruption techniques are non-selective in that the cell wall is attacked at multiple locations leading to the formation of small cell wall fragments. This increases the downstream purification burden because such fragments are difficult to separate from the process stream and may lead to the fouling of adsorbents and the clogging of chromatographic columns (steps 3 and 4 above). While such cell disruption is not usually a requirement in the recovery of intracellular proteins, in most conventional processes, cell wall fragmentation is a consequence.
It is an object of the invention to provide a method and an apparatus for extracting material from cells, which method avoids the above-mentioned drawbacks.
Another object of the invention is to provide a method for microbial cell disruption that reduces cell wall fragmentation.
Still another object of the invention is to provide a method of cell disruption which only minimally exposes the cells to high shear forces and little or no heat generation.
Yet another object of the invention is to provide an improved method of microbial cell disruption that simplifies the purification scheme, reduces processing time and favorably impacts production costs.
These and other objects are achieved by the methods and apparatus of the invention.